Revert "[clang] Improved canonicalization for template specialization types" (#135354)

Reverts #135119 because of the assert in ASTContext.cpp, line 5619.
See #135352 for details.

Author: slydiman

clang-tools-extra/clangd/AST.cpp

@@ -439,8 +439,7 @@ QualType declaredType(const TypeDecl *D) {
   if (const auto *CTSD = llvm::dyn_cast<ClassTemplateSpecializationDecl>(D))
     if (const auto *Args = CTSD->getTemplateArgsAsWritten())
       return Context.getTemplateSpecializationType(
-          TemplateName(CTSD->getSpecializedTemplate()), Args->arguments(),
-          /*CanonicalArgs=*/std::nullopt);
+          TemplateName(CTSD->getSpecializedTemplate()), Args->arguments());
   return Context.getTypeDeclType(D);
 }
 

clang/docs/ReleaseNotes.rst

@@ -301,8 +301,6 @@ Improvements to Clang's diagnostics
 - Clang now better preserves the sugared types of pointers to member.
 - Clang now better preserves the presence of the template keyword with dependent
   prefixes.
-- Clang now in more cases avoids printing 'type-parameter-X-X' instead of the name of
-  the template parameter.
 - Clang now respects the current language mode when printing expressions in
   diagnostics. This fixes a bunch of `bool` being printed as `_Bool`, and also
   a bunch of HLSL types being printed as their C++ equivalents.

clang/include/clang/AST/ASTContext.h

@@ -367,6 +367,9 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                      const ASTContext&>
     CanonTemplateTemplateParms;
 
+  TemplateTemplateParmDecl *
+    getCanonicalTemplateTemplateParmDecl(TemplateTemplateParmDecl *TTP) const;
+
   /// The typedef for the __int128_t type.
   mutable TypedefDecl *Int128Decl = nullptr;
 
@@ -1808,26 +1811,22 @@ class ASTContext : public RefCountedBase<ASTContext> {
                           bool ParameterPack,
                           TemplateTypeParmDecl *ParmDecl = nullptr) const;
 
-  QualType getCanonicalTemplateSpecializationType(
-      TemplateName T, ArrayRef<TemplateArgument> CanonicalArgs) const;
+  QualType getTemplateSpecializationType(TemplateName T,
+                                         ArrayRef<TemplateArgument> Args,
+                                         QualType Canon = QualType()) const;
 
   QualType
-  getTemplateSpecializationType(TemplateName T,
-                                ArrayRef<TemplateArgument> SpecifiedArgs,
-                                ArrayRef<TemplateArgument> CanonicalArgs,
-                                QualType Underlying = QualType()) const;
+  getCanonicalTemplateSpecializationType(TemplateName T,
+                                         ArrayRef<TemplateArgument> Args) const;
 
-  QualType
-  getTemplateSpecializationType(TemplateName T,
-                                ArrayRef<TemplateArgumentLoc> SpecifiedArgs,
-                                ArrayRef<TemplateArgument> CanonicalArgs,
-                                QualType Canon = QualType()) const;
+  QualType getTemplateSpecializationType(TemplateName T,
+                                         ArrayRef<TemplateArgumentLoc> Args,
+                                         QualType Canon = QualType()) const;
 
-  TypeSourceInfo *getTemplateSpecializationTypeInfo(
-      TemplateName T, SourceLocation TLoc,
-      const TemplateArgumentListInfo &SpecifiedArgs,
-      ArrayRef<TemplateArgument> CanonicalArgs,
-      QualType Canon = QualType()) const;
+  TypeSourceInfo *
+  getTemplateSpecializationTypeInfo(TemplateName T, SourceLocation TLoc,
+                                    const TemplateArgumentListInfo &Args,
+                                    QualType Canon = QualType()) const;
 
   QualType getParenType(QualType NamedType) const;
 
@@ -2943,21 +2942,6 @@ class ASTContext : public RefCountedBase<ASTContext> {
   TemplateArgument getCanonicalTemplateArgument(const TemplateArgument &Arg)
     const;
 
-  /// Canonicalize the given template argument list.
-  ///
-  /// Returns true if any arguments were non-canonical, false otherwise.
-  bool
-  canonicalizeTemplateArguments(MutableArrayRef<TemplateArgument> Args) const;
-
-  /// Canonicalize the given TemplateTemplateParmDecl.
-  TemplateTemplateParmDecl *
-  getCanonicalTemplateTemplateParmDecl(TemplateTemplateParmDecl *TTP) const;
-
-  TemplateTemplateParmDecl *findCanonicalTemplateTemplateParmDeclInternal(
-      TemplateTemplateParmDecl *TTP) const;
-  TemplateTemplateParmDecl *insertCanonicalTemplateTemplateParmDeclInternal(
-      TemplateTemplateParmDecl *CanonTTP) const;
-
   /// Type Query functions.  If the type is an instance of the specified class,
   /// return the Type pointer for the underlying maximally pretty type.  This
   /// is a member of ASTContext because this may need to do some amount of

clang/include/clang/AST/PropertiesBase.td

@@ -877,14 +877,11 @@ let Class = PropertyTypeCase<TemplateArgument, "Expression"> in {
   def : Property<"expression", ExprRef> {
     let Read = [{ node.getAsExpr() }];
   }
-  def : Property<"IsCanonical", Bool> {
-    let Read = [{ node.isCanonicalExpr() }];
-  }
   def : Property<"isDefaulted", Bool> {
     let Read = [{ node.getIsDefaulted() }];
   }
   def : Creator<[{
-    return TemplateArgument(expression, IsCanonical, isDefaulted);
+    return TemplateArgument(expression, isDefaulted);
   }]>;
 }
 let Class = PropertyTypeCase<TemplateArgument, "Pack"> in {

clang/include/clang/AST/TemplateBase.h

@@ -167,8 +167,6 @@ class TemplateArgument {
     unsigned Kind : 31;
     LLVM_PREFERRED_TYPE(bool)
     unsigned IsDefaulted : 1;
-    LLVM_PREFERRED_TYPE(bool)
-    unsigned IsCanonicalExpr : 1;
     uintptr_t V;
   };
   union {
@@ -189,8 +187,7 @@ class TemplateArgument {
 
 public:
   /// Construct an empty, invalid template argument.
-  constexpr TemplateArgument()
-      : TypeOrValue{Null, /*IsDefaulted=*/0, /*IsCanonicalExpr=*/0, /*V=*/0} {}
+  constexpr TemplateArgument() : TypeOrValue({Null, 0, /* IsDefaulted */ 0}) {}
 
   /// Construct a template type argument.
   TemplateArgument(QualType T, bool isNullPtr = false,
@@ -265,10 +262,9 @@ class TemplateArgument {
   /// This form of template argument only occurs in template argument
   /// lists used for dependent types and for expression; it will not
   /// occur in a non-dependent, canonical template argument list.
-  TemplateArgument(Expr *E, bool IsCanonical, bool IsDefaulted = false) {
+  explicit TemplateArgument(Expr *E, bool IsDefaulted = false) {
     TypeOrValue.Kind = Expression;
     TypeOrValue.IsDefaulted = IsDefaulted;
-    TypeOrValue.IsCanonicalExpr = IsCanonical;
     TypeOrValue.V = reinterpret_cast<uintptr_t>(E);
   }
 
@@ -411,11 +407,6 @@ class TemplateArgument {
     return reinterpret_cast<Expr *>(TypeOrValue.V);
   }
 
-  bool isCanonicalExpr() const {
-    assert(getKind() == Expression && "Unexpected kind");
-    return TypeOrValue.IsCanonicalExpr;
-  }
-
   /// Iterator that traverses the elements of a template argument pack.
   using pack_iterator = const TemplateArgument *;
 

clang/include/clang/AST/Type.h

@@ -6676,9 +6676,10 @@ class TemplateSpecializationType : public Type, public llvm::FoldingSetNode {
   /// replacement must, recursively, be one of these).
   TemplateName Template;
 
-  TemplateSpecializationType(TemplateName T, bool IsAlias,
+  TemplateSpecializationType(TemplateName T,
                              ArrayRef<TemplateArgument> Args,
-                             QualType Underlying);
+                             QualType Canon,
+                             QualType Aliased);
 
 public:
   /// Determine whether any of the given template arguments are dependent.
@@ -6746,7 +6747,7 @@ class TemplateSpecializationType : public Type, public llvm::FoldingSetNode {
 
   void Profile(llvm::FoldingSetNodeID &ID, const ASTContext &Ctx);
   static void Profile(llvm::FoldingSetNodeID &ID, TemplateName T,
-                      ArrayRef<TemplateArgument> Args, QualType Underlying,
+                      ArrayRef<TemplateArgument> Args,
                       const ASTContext &Context);
 
   static bool classof(const Type *T) {

clang/include/clang/AST/TypeProperties.td

@@ -737,19 +737,39 @@ let Class = DependentAddressSpaceType in {
 }
 
 let Class = TemplateSpecializationType in {
+  def : Property<"dependent", Bool> {
+    let Read = [{ node->isDependentType() }];
+  }
   def : Property<"templateName", TemplateName> {
     let Read = [{ node->getTemplateName() }];
   }
-  def : Property<"args", Array<TemplateArgument>> {
+  def : Property<"templateArguments", Array<TemplateArgument>> {
     let Read = [{ node->template_arguments() }];
   }
-  def : Property<"UnderlyingType", QualType> {
-    let Read = [{ node->isCanonicalUnqualified() ? QualType() :
-                                                   node->desugar() }];
+  def : Property<"underlyingType", Optional<QualType>> {
+    let Read = [{
+      node->isTypeAlias()
+        ? std::optional<QualType>(node->getAliasedType())
+        : node->isCanonicalUnqualified()
+            ? std::nullopt
+            : std::optional<QualType>(node->getCanonicalTypeInternal())
+    }];
   }
 
   def : Creator<[{
-    return ctx.getTemplateSpecializationType(templateName, args, std::nullopt, UnderlyingType);
+    QualType result;
+    if (!underlyingType) {
+      result = ctx.getCanonicalTemplateSpecializationType(templateName,
+                                                          templateArguments);
+    } else {
+      result = ctx.getTemplateSpecializationType(templateName,
+                                                 templateArguments,
+                                                 *underlyingType);
+    }
+    if (dependent)
+      const_cast<Type *>(result.getTypePtr())
+          ->addDependence(TypeDependence::DependentInstantiation);
+    return result;
   }]>;
 }